i really don't know maybe in the late 70's.. the ihc engines were mostly light blue dt-466 dt-444, in the 90's.... and the maxxforce family are black.. i never seen dark blue. sorry i rubbed my nose on some and they are black.
i been told that other manufacturer engines--cat,cummins-detroit-- were painted red in ihc trucks.
they were painted white in pete's&kw's [ cummins.cat,detroit]